32 BULLETIN 1118, U. .S. DEPARTMENT OF AGRICULTURE. 
by injurious or even disastrous effects from later insect attack. 
Bordeaux mixture is the most effective spray against scab, and 
when made up with lake or shallow well (soft) water spray injury 
seldom follows. Usually deep well (hard) water is satisfactory, 
but a few instances are on record where a moderate amount of spray 
burn has resulted from Bordeaux mixture being made up with such 
water and applied on citrus trees. In certain localities hard water 
can be used with safety, while in others it is likely to be followed 
by more or less spray burn. Unless extra applications of insecticides 
are made, scale insects are very likely to increase rapidly and do 
great damage following this spray. Commercial Bordeaux prepara- 
tions (Wallace, 31) when used in sufficient quantities to give about 
three-sixteenths of 1 per cent copper in the diluted spray are effective 
though expensive substitutes for homemade Bordeaux mixture. 
Bordeaux mixture plus oil emulsion is equally as effective against 
citrus scab as is plain Bordeaux mixture and against insects as 
is the same strength of oil emulsion when applied separately. 
The fungicidal effects outlast the insecticidal effect, and for this 
reason the usual treatment and sometimes extra applications for 
scale are required following the use of Bordeaux mixture plus oil 
emulsion. Burgundy mixture is quite effective against citrus scab, 
but if not carefully made is likely to cause some injury to fruit or 
foliage. This spray is considered too risky for general use. Scale 
insects become very numerous following applications of this material. 
Amnionic al copper carbonate solution is much less effective against 
citrus scab than is Bordeaux mixture. In general, it is not a desir- 
able spray for scab control. Scale insects increase considerably fol- 
lowing its use. Lime-sulphur solution, 32° B., diluted 1 to 40, is 
not more than 50 per cent effective against severe scab infection, 
but for certain reasons it can be applied profitably in many orchards. 
No spray injury has been observed where this material was used 
during the spring for scab control. This spray kills red spiders, 
rust mites, and scale crawlers. Dry lime-sulphur and barium sul- 
phur when used on the basis of sulphur equivalents of standard 
lime-sulphur solution, seem to be fairly satisfactory but quite ex- 
pensive substitutes for the commercial lime-sulphur solution. Soda- 
sulphur or sodium-sulphur compounds are expensive and compara- 
tively ineffective substitutes for lime-sulphur solution for use against 
scab. The hazard of spray burn is especially great following the 
use of sodium-sulphur compounds of fungicidal strengths. 
Dusting for the control of citrus scab has not been tested thor- 
oughly. There seems to be no good reason for assuming that dusting 
with materials now used will prove as effective or as practical as 
spraying. 
